Cope with newer Xcode not having the 10.6 SDK.

The latest Xcode, as of today, has only 10.9 and 10.10 SDKs, which means
that, if we build Wireshark and request a deployment minimum release of
10.6, we'll be building against an SDK in which libpcap has routines
that aren't available in 10.6 and that doesn't use weak linking for
them, so the resulting binary won't actually work on 10.6.

Use the run-time loader to find those routines (currently, only
pcap_set_tstamp_precision()) and call them only if we find them.

On other UN*Xes, we still assume that we'll be running only on the
release against which we were built and newer releases.

Change-Id: Iab20d86fe3be4b299cfb6e25c1f95dc6e1581661
Reviewed-on: https://code.wireshark.org/review/5120
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 59 insertions, 5 deletions

diff --git a/caputils/capture-pcap-util-unix.c b/caputils/capture-pcap-util-unix.c
index 8aae100c33..33047317d5 100644
--- a/caputils/capture-pcap-util-unix.c
+++ b/caputils/capture-pcap-util-unix.c
@@ -26,11 +26,13 @@
 
 #ifdef HAVE_LIBPCAP
 
-#ifdef HAVE_PCAP_FINDALLDEVS
-
 #include <pcap.h>
 
-#else /* HAVE_PCAP_FINDALLDEVS */
+#ifdef __APPLE__
+#include <dlfcn.h>
+#endif
+
+#ifndef HAVE_PCAP_FINDALLDEVS
 
 #include <stdlib.h>
 #include <string.h>
@@ -60,8 +62,6 @@ struct rtentry;
 # include <sys/sockio.h>
 #endif
 
-#include "caputils/capture-pcap-util.h"
-
 #endif  /* HAVE_PCAP_FINDALLDEVS */
 
 #ifdef HAVE_LIBCAP
@@ -334,6 +334,60 @@ cant_get_if_list_error_message(const char *err_str)
 	return g_strdup_printf("Can't get list of interfaces: %s", err_str);
 }
 
+#ifdef HAVE_PCAP_SET_TSTAMP_PRECISION
+/*
+ * Request high-resolution time stamps.
+ *
+ * We don't check for errors - if this fails, we just live with boring old
+ * microsecond-resolution time stamps. The only errors pcap_set_tstamp_precision()
+ * is documenting as returning are PCAP_ERROR_TSTAMP_PRECISION_NOTSUP, which just
+ * means we can't do nanosecond precision on this adapter, in which case we
+ * just live with whatever resolution we get by default, and
+ * PCAP_ERROR_ACTIVATED, which shouldn't happen as we shouldn't call this
+ * after we've activated the pcap_t.
+ */
+void
+request_high_resolution_timestamp(pcap_t *pcap_h)
+{
+#ifdef __APPLE__
+	/*
+	 * On OS X, if you build with a newer SDK, pcap_set_tstamp_precision()
+	 * is available, so the code will be built with it.
+	 *
+	 * However, if you then try to run on an older release that
+	 * doesn't have pcap_set_tstamp_precision(), the dynamic linker
+	 * will fail, as it won't find pcap_set_tstamp_precision().
+	 *
+	 * libpcap doesn't use OS X "weak linking" for new routines,
+	 * so we can't just check whether a pointer to
+	 * pcap_set_tstamp_precision() is null and, if it is, not
+	 * call it.  We have to, instead, use dlopen() to load
+	 * libpcap, and dlsym() to find a pointer to pcap_set_tstamp_precision(),
+	 * and if we find the pointer, call it.
+	 */
+	static gboolean initialized = FALSE;
+	static void *libpcap_handle;
+	static int (*p_pcap_set_tstamp_precision)(pcap_t *, int);
+
+	if (!initialized) {
+		p_pcap_set_tstamp_precision =
+		    (int (*)(pcap_t *, int))
+		      dlsym(RTLD_NEXT, "pcap_set_tstamp_precision");
+		initialized = TRUE;
+	}
+	if (p_pcap_set_tstamp_precision != NULL)
+		(*p_pcap_set_tstamp_precision)(pcap_h, PCAP_TSTAMP_PRECISION_NANO);
+#else /* __APPLE__ */
+	/*
+	 * On other UN*Xes we require that we be run on an OS version
+	 * with a libpcap equal to or later than the version with which
+	 * we were built.
+	 */
+	pcap_set_tstamp_precision(pcap_h, PCAP_TSTAMP_PRECISION_NANO);
+#endif /* __APPLE__ */
+}
+#endif /* HAVE_PCAP_SET_TSTAMP_PRECISION */
+
 /*
  * Get the versions of libpcap, libpcap, and libnl with which we were
  * compiled, and append them to a GString.